Fuel control for fluid fuel burners



A. N. SCHREUDER FUEL CONTROL FOR FLUID FUEL BURNERS April 1, 1941.

Filed July 14, 1938 W, i; 0% m D 110 VOLT April 1941- A. N. SCHREUDER2.237.041

FUEL CONTROL FOR FLUID FUEL BURNERS Filed July 14, 1938 s Sheets-Sheet3' i7" IIO VOLT Patented Apr. 1, 1941 UNITED STATES PATENT OFFICE FUELCONTROL FOR FLUID FUEL BURNERS Application July 14, 1938, Serial No.219,269

16 Claims.

My invention relates to an improvement incontrol means for burners andis herein shown as applied to liquid hydrocarbon burners of a knowntype.

One purpose is the provision of means for increasing and reducing airpressure in a hydrocarbon burner independently of fan or motor speed.

Another purpose is the provision of safety means for cutting off thefuel feed to such a burner when the fan or motor circuit is broken orthe fan ceases to operate.

Another purpose is the provision of improved switch means forcontrolling the operation of such a burner.

Another purpose is the provision of improved means for controlling thedelivery of liquid fuel to such a burner.

Another purpose is the provision of means for employing an air pressureresponsive element to control the operation of a liquid hydrocarbonburner.

Other purposes will appear from time to time during the course of thespecification and claims.

I illustrate my invention more or less diagrammatically in theaccompanying drawings wherein:

Figure 1 is a front elevation; Figure 2 is a section on the line 22 ofFigure Figure 3 is a fragmentary view of a portion of the structureshown in Figures 1 and 2;

Figure 4 is a section on the line 44 of Figure 3- Figure 5 is a viewsimilar to Figure 4 with the parts in a different position;

Figure 6 is a wiring diagram; and

Figure 7 is a wiring diagram illustrating a variation.

Like parts are indicated by like characters throughout the specificationand drawings.

Referring to the drawings, I indicates any suitable base or support uponwhich is mounted a stove or furnace shell generaly indicated as 2.

Within said shell, the details of which form no part of the presentinvention, is located an inner heater drum 3. Mounted within the drum isa pot 4 having a plurality of air inlet apertures 5 through which air issupplied for mixture within the pot with liquid hydrocarbon suppliedalong the line 6. It will be observed from Figure 2 that the lquidhydrocarbon is delivered to the concave bottom I of the pot 4 and itwill be understood that the hydrocarbon is vaporized by the heat ofcombustion in or above the pot and the vaporized i hydrocarbon is mixedwith the air flowing in through the apertures 5 and is thereafterburned. 8 indicates a baiile located beneath the pot and herein shown ascentrally apertured as at 9, the air supply being delivered through theaperture 9, as will later appear. l0 indicates a pilot ring.

I] diagrammatically illustrates any suitable valve member or mechanism,the details of which do not of themselves form part of the presentinvention. It will be understood that it includes a variable means forproviding a maximum and a minimum and an intermediate flow of liquidhydrocarbon fuel. It will be understood that at minimum settingsuflicient fuel is supplied along the line 6 to maintain combustion at alow or pilot stage. At that time the pilot ring Ill is eifective. Forthe intermediate and high fires, the air admitted through the apertures5 below the pilot ring It! serves as primary air which, when mixed withthe vaporized hydrocarbon, rises through the central aperture of thepilot ring In and is burned upon mixture with the secondary air flowingthrough the holes 5 above the pilot ring l0.

As indicating practical means of providing this three-stage flow, Iillustrate in the wiring diagram of Figure 6 two oil valve members l2and I3. When one of these valves is in closed position and one open, anintermediate supply is delivered; when both are in open position, amaximum supply is delivered. It will be understood that when both valvesare closed, appropriate means are provided, by by-pass or otherwise, formaintaining the above mentioned minimum fuel supply.

It generally indicates a shell or scroll blower actuated by a motorlocated within the housing I5. Any suitable fan not herein shown isassociated with the motor and it will be understood that when the belowdescribed motor circuit is closed, the motor within the housing I5 iseffective to rotate the fan and to cause a supply of air to enter thechamber A beneath the partition 8, which air supply passes upwardlythrough the aperture 9 to the space between the shell 3 and the pot 4.

In order to vary the pressure within the chamber A and thus to vary theair delivery to the burner, I provide an additional air port including apassage housing generally indicated as 16. I! indicates any suitableconnection between it and the chamber A. Pivoted in the opening l8 ofthe passage housing is a shutter 0r galte generally indicated as N!which is provided with ears 20 which rest in slots 2| which serve aspivots. 22 indicates any suitable weight or weights tending to bias thegate |9 to the open position in which it is shown in Figure 4. Anysuitable means may be employed for limiting the counterclockwise tiltingmovement of the shutter I9 in response to the weight 22. The position inwhich it is shown in Figure 4 is an example of a satisfactory maximumopening position.

23 indicates a bracket in the end of which is adjustably mounted thescrew 24 the head 25 of which serves as an abutment the purpose of vwhich will later appear.

26 is an additional housing mounted on the side of the passage housingI6. 21 is a bracket, secured to the housing 26, to which bracket issecured the bimetallic loop 28 shown as generally cylindrical orcircular in form. It terminates in a generally radial extension 29 towhich is secured an insulating bar 38. Mounted on said bar is a contact3| having a conductive connection 32. Additionally mounted on it is aflexible leaf 33 of conductive material in circuit with the line 34. Theleaf 33 is provided with a contact 35 adapted to be opposed to thecontact 3|, and which is in line to be engaged by the head 25 of thescrew 24 in such fashion that a rotation in a clockwise direction of theshutter or gate l9 causes a closure of a circuit, which causes aconductive contact between the members 3| and 35 and thus /puts the line32 and 34 in circuit. Located with- .{in the loop or interior of thebimetallic member '28 is a resistant heating element or coil 36 havingconductors 31, 38.

It will be understood that when the heater 36 is heated, it causes aflexure of the member 28 which moves the member to the right, referringto the position of the parts in Figure 4. This movement of theinsulating bar 30 can be adjustably limited by the employment of thescrew stop 39 adjustable in any suitable abutment 48. Preferably theparts are so adjusted that the member 38 cannot be flexed sufficientlyto the right to permit a contact between the members 3| and to be brokenwhen the gate is in the closed position in which it is shown in Figure5.

Referring to the wiring diagram of Figure 6, 4| generally indicates aroom thermostat structure having a contact strip 42, the position ofwhich may be controlled in response to variations in room temperature,as by the bimetallic coil 43. 44 is the main line contact in circuitwith the main line conductor 45 which extends to the secondary coil 46of the transformer C. 41 is an intermediate contact in circuit with theline 48, which extends to the heating coil 43, which surrounds oraffects a bimetallic strip 50 which controls any suitable valve plunger|2 already referred to. The line continues as at 48a to the line 32 ofthe contact 3| on the insulating part 30. Extending from the line 48 isa shunt connection 481) to the heating coil 5|, which controls thebimetallic strip 52 which actuates a switch 53, which controls actuatingcircuit 54, 55 for the motor l5, which lines extend to any suitablesource of electric power, as at D.

If desired. a manually controllable switch 56 may be in circuit to breakall of the above described connections. The line 481) extends beyond theheater 5| to the secondary coil 46 of the transformer C where it mayjoin the line 34 at a common terminal. 60 is an additional contact onthe thermostat 4| from which leads the line 3'! which extends to theheating coil 36 for the bimetallic loop 28 (Figs. 4 and 5) The line 38extends beyond the coil 36 to an additional heating coil 6| and extendstherebeyond through line 38a and line 32 to the contact 3|. The coil 6|controls a bimetallic strip 62 which controls the second oil valve l3already mentioned. The primary coil 46a of the transformer C isconnected across the lines 54, 55 in parallel with the motor.

It will be understood that the heater above described may be run atthree stages. First, a pilot stage in which a minimum oil supply issupplied and the oil valves l2 and I3 are both closed. At this stage thefan is inactive and the weights 22 will hold the shutter IS in the openposition in which it is shown in Figure 4, and the burner will run atnatural draft. The bulk of the air supply will flow through the inletl8, but some may flow through the fan. In any event, there is no forceddraft and preferably only sufficient combustion is maintained to providea pilot for intermediate or full combustion.

If an intermediate fire is desired, or if the device is operated by theroom thermostat, the leaf 42 bridges the contacts 44, 41. In the formherein shown, as in Figure 6, this bridging or circuit closing takesplace in response to the fiexure of the member 43 as the roomtemperature drops. The initial result of the closure is as follows.Current flows through the coil 5| and flexes the leaf 52. This closesthe switch 53, which closes the motor circuit and causes the motor andfan to operate. The motor operation causes a delivery of air into thespace A and upwardly about the pot 4. This air reaches the interior ofthe pot through the apertures 5, giving an increased air supply. At thesame time, the baflie 65 in the housing I6 is effective to direct ablast or current of air against the lower half of the shutter l9. Thiscloses or tends to close the shutter against the gravital action of theweights 22. As the shutter closes, the contact 25 on the shutter engagesthe flexible leaf 33 and closes the contacts 3|, 35. This closes thecircuit through the heater 49 and by flexing upwardly the bimetallicstrip 58 raises the oil valve |2-and admits an additional supply of oilto the bottom of the not 4. The member 38 acts as a stop and prevents acomplete closure of the shutter I9, so some of the air pressure isrelieved through the aperture l8 and the full effect of the fan is,therefore, not felt in the not 4. In other words, an intermediate ratherthan a full supply of air is delivered to the pot 4 to burn theintermediate supply of oil which is admitted by lifting the valve l2,the valve l3 being still closed.

An additional drop of the room temperature, or a manual closure, closesa further circuit between the contacts 44 and 68. One effect of thisadditional closure is to heat the resistance 36 andto cause theinsulating bar 30 to move to the right. as shown in Figure 4, inresponse to the flexure of the bimetallic loop 28. Continued airpressure within the chamber A and the housing |6 causes the shutter ii!to follow the bar 30 as it recedes, keeping the switch contacts 3| and35 closed. The parts are preferably so set that the shutter I9 issubstantially completely closed, as shown in Figure 5, thus preventingany relief of the air pressure within the space A and about the not 4.As above mentioned, the stop 39 is so set as to prevent such a furtherrecession of the member 30 as would break the contact between themembers 3| and 35. A further result of a bridging of the contacts 44 and6D is the heating of the coil 6|, which causes a flexure of the strip62, which in turn lifts the maximum oil supply valve l3. Thus a. fullmaximum supply' of oil is provided, and since any eflective escape ofair through the aperture [8 is prevented, the air pressure and airdelivery are correspondingly stepped up, a maximum supply of air beingprovided for the combustion of the maximum supply of oil.

When a change is made from maximum combustion to intermediatecombustion, and from intermediate combustion to pilot combustion, thereis a reversal of the above described action. Assume that in response tothermostatic control or to manual operation the contact is brokenbetween the contacts 44 and 60, the result is a'deenergization of thecoils 36 and BI, without affecting, however, the motor circuit. As thecoil 36 cools, the bar 30 takes a counter-clockwise movement, referringto Figure 4, and partially opens the shutter i9 and permits a reductionof air pressure within the space A and thus a reduction of air supply tothe pot 4. At the same time, the oil valve I3 is closed and the deviceis restored to intermediate operation. It will be noted that theincrease and reduction of air pressure or air supply, as the oil supplypasses from intermediate to maximum, or drops from maximum tointermediate, is obtained without affecting the operation of the fan ormotor at all.

Assuming that the device is on intermediate fire and that eithermanually or thermostatically the contact between the members 44 and 41is broken, this causes a de-energization of the resistance which permitsa breaking of the motor circuit switch 53. It also causes a deenergization of the coil 49 which controls the valve I2. The motor,therefore, stops running and the valve l2 closes, and the shutter l9drops to the fully open position in which it is shown in Figure 4. Themotor circuit cuts out immediately upon the opening of switch 53 but thevalve i2 is closed more slowly due to the time lag required for thecooling of bimetallic member 50. Any temporary excess supply of oil isamply taken care of under the natural draft condition. as suflicient airis admitted through the aperture [8 to prevent any carbon deposit or anysooting up of the burner. This is possible because the maximum oil valvei3 has already been closed and the drop from intermediate oil supply tominimum oil supply does not cause any carbon deposit and does not admitinto the bottom of the pot 4 any more oil than can readily be burned offby a natural draft.

It will be realized that whereas I have described and shown a practicaland operative device, nevertheless many changes may be made in size,shape, number, disposition and relationship of parts without departingfrom the spir t of my invention. For example, as shown in F gure 7, Imay employ a circuit in which the fan is in operation at all stages ofcombustion from the pilot stage up.

As illustrated in the diagram, the motor I5 is electrically connected bylines 54a and 55a to the service lines 54 and 55, respectively. Both themotor and the transformer C are manually controlled by the switch 56.The electrical connections are identical with those in the electricaldiagram of Figure 6 and are indicated by like numerals, with theexception that the line 48b, the heating coil 5|, and the associatedbimetallic strip 52 and motor switch 53 are omitted. It will be realizedthat in the first or pilot stage, the shutter IS, with the motor inoperation, assumes the intermediate positi n b ve described with thecontacts 3| and 35 closed. When the room thermostat functions and closesthe contacts 44 and 41, the heater coil 43 is energized and opens thevalve 12 for an intermediate fire. However, the shutter remains inintermediate position.

It will be observed in both forms that the switch structure, includingthe contacts 3| and 35, serves as a safety device which cuts out thewhole operating circuit in the event that the motor circuit is broken orthe fan ceases to operate. It is necessary for the fan to be inoperation in order to maintain the contacts 38 and 35 in contact, asotherwise the weights 22 pull the shutter into fully open position, andpermit the leaf 33 to flex into circuit breaking condition. Thisprovides a positive safety device which makes it impossible for anythingmore than a minimum oil supply to be delivered if the fan is notoperating, and this minimum oil supply can be burned off by naturaldraft and will maintain at least a pilot flame in both forms of thedevice without causing sooting up or carbon deposit. In no event can anexcess supply of oil flow into the pot 4, a supply too great for theavailable air to burn it off. This prevents flooding of the pot andescape of excess oil from the burner, with the consequent fire hazardwhich is present in so many prior art burners.

It will be understood that whereas I have shown my invention as appliedto a furnace unit, it may be employed in connection with any duct usedin connection with any furnace or burner, and may for example beemployed in a conversion burner or unit, or in a burner completelyhoused outside of a heating plant. Also, it will be understood that Imay employ a wide variety of switch mechanisms in the place of thoseshown, and may for example employ a mercury tube switch.

I claim:

1. In combination, a burner, passage means for delivering a fluid fuelto said burner, means for delivering air under pressure to said burner,a motor for actuating said air delivery means, an actuating circuit forsaid motor, an air admission member adapted to admit air under naturaldraft to the burner when said air delivery means is not operating, andadapted to permit the escape of a portion of the air under pressure, andthereby to reduce the pressure of the air delivered to the burner, whensaid air delivery means is operating, shutter means for said airadmission member, and temperaturecontrolled means for setting theposition of said shutter means and controlling the fuel delivery meansso that the shutter will be closed and the fuel flow increased as thetemperature falls.

2. In combination, a burner, passage means for delivering a fluid fuelto said burner, means for delivering air under pressure to said burner,a motor for actuating said air delivery means, an actuating circuit forsaid motor, an air admission member adapted to admit air under naturaldraft to the burner when said air delivery means is not operating, andadapted to permit the escape of a portion of the air under pressure, andthereby to reduce the-pressure of the air delivered to the burner, whensaid air delivery means is operating, shutter means for said airadmission member, responsive to air pressure created by the air deliverymeans, and means for controlling the fuel delivery means in response tomovement of said shutter means. including a switch having a pair ofnormally separated contacts, and means for closing said contacts inresponse to movement of said shutter means.

3. In combination, a burner, passage means for delivering a fluid fuelto said burner, means for controlling the flow of fuel through saidpassage means in a plurality of stages, including a minimum flow, anintermediate flow, and a maximum flow, means for delivering air underpressure to said burner, a motor for actuating said air delivery means,an actuating circuit for said motor, an additional air port adapted to,

admit air under natural draft to the burner, when said motor driven airdelivery means is not operating, and adapted to permit the escape of airunder pressure, and thereby to reduce the pressure of the air deliveredto the burner, when the motor driven air delivery means is operating,normally open shutter means for said additional port, said shutter meansbeing movable toward closed position by air pressure created by the saidair delivery means, a multiple contact room thermostat including atemperature responsive member, a pair of contacts adapted for initialclosure thereby, and an additional contact adapted for subsequentclosure, a control' circuit including said initial two contacts, meansfor closing the motor circuit in response to closure of said controlcircuit, means in said control circuit adapted to increase the flow 'offuel from minimum flow to intermediate flow, an additional circuitincluding said third contact, means in said additional circuit efiectivewhen said circuit is closed to increase the flow of fuel fromintermediate flow to maximum flow, limit means for said shutter adaptedto prevent its complete closure when the circuit including the initialtwo contacts is closed, and means, responsive to the closure of theadditional circuit including the third contact, effective to move saidlimit means and to permit a further closing movement of said shutter,and thereby to increase the air pressure adjacent the burner chamber.

4. In combination, a burner, passage means for delivering afluid fuel tosaid burner, means for controlling the flow of fuel through said passagemeans in a plurality of stages, including a minimum flow, anintermediate flow, and a maximum flow, means for delivering air underpressure to said burner, a motor for actuating said air delivery means,an actuating circuitfor said motor, an additional air port adapted to'admit air under natural draft to the burner, when said motor driven airdelivery means is not operating, and adapted to permit the esca e of airunder pressure. and thereby to reduce the pressure of the air deliveredto the burner, when the motor driven air delivery means is ,operatinnormally open shutter means for said additional port, said shutter meansbeing movable toward closed position by air pressure created by the airdelivery means, stop means for limitinP. this closing movement of theshutter. a multiple contact room thermostat including a temperatureresponsive member, a pair of contacts adapted for initial closurethereby, and an additional contact adapted for subsequent closure, acontrol circuit including said initial two contacts. means for closingthe motor circuit in response to closure of said contact circuit, meansin said control circuit adapted to increase the flow of fuel fromminimum flow to intermediate flow, an additional circuit including saidthird contact, means in said additional circuit eifective when saidcircuit is closed to increase the flow of fuel from intermediate flow tomaximum flow, other means in said last circuit for moving the stop meansto permit further closing movement of the shutter and means responsiveto an opening movement of said shutter for reducing the flow of fuelwhen the motor driven air delivery means is not operating.

5. In combination, a burner, means for supplying a fluid fuel to theburner including a valve'for adjusting the rate of fuel supply, meansincluding a blower for supplying combustion air to the burner, anauxiliary air port communicating with the burner for admitting air undernatural draft when the blower is not operating and permitting the escapeof a portion of the air under pressure from the blower when the bloweris operating, movable damper means associated with said port forcontrolling the supply of air to the burner, and means forsimultaneously adjusting the fuel-valve and the position of thedamper-means.

6. In combination, a burner, means for supplying a fluid fuel to theburner including a valve for adjusting the rate of fuel supply, meansincluding a blower for supplying combustion air to the burner, anauxiliary air port communicating with the burner for admitting air undernatural draft when the blower is not operating and permitting the escapeof a portion of the air under pressure from the blower when the bloweris operating, movable damper means associated with said port forcontrolling the supply of air to the burner, and temperature-controlledmeans for simultaneously adjusting the fuel-valve and the position ofthe damper means.

'7. In combination, a burner, means for supplying a fluid fuel to theburner including a valve for adjustingthe rate of fuel supply, meansincluding a blower for supplying combustion air to the burner, anauxiliary air port communicating with the burner for admitting air undernatural draft when the blower is not operating and permitting the escapeof a portion of the air under pressure from the blower when the bloweris operating, a self-opening shutter for said port, andtemperature-controlled means for simultaneously and progressivelyopening the fuel valve and closing said shutter.

8. In combination, a burner, means for supplying a fluid fuel to theburner including a valve for adjusting the rate of fuel supply, meansincluding a blower for supplying combustion air to the burner, anauxiliary air port communicating with the burner for admitting air undernatural draft when the blower is not operating and permitting the escapeof a portion of the air under pressure from the blower when the bloweris operating, a self-opening shutter for said port, said shutter beingclosed by air under pressure from the blower, and temperaturecontrolledmeans for simultaneously limiting the closing movement of the shutterand proportionately opening the fuel-valve.

9. In combination, a burner, means for delivering a fluid fuel to'theburner, valve means controlling the flow of fuel to the burner, meansincluding a blower for delivering air under pressure to the burner,means including a passage for either admitting air under natural-draftto the burner or functioning to permit the escape of a portion of theair under pressure from the blower, normally open damper-means foropening or closing said passage, and means effective only while theblower is operating for substantially simultaneously adjusting saidvalve-means to increase the fuel flow and adjusting said damper-meanstoward closed position to increase the air supply to the burner.

10. In combination, a burner, means for delivering a fluid fuel to theburner, valve-means controlling the flow of fuel to the burner, meansincluding a blower for delivering air under pressure to the burner,means including a passage for either admitting air under natural-draftto the burner or functioning to permit the escape of a portion of theair under pressure from the blower, normally open damper-means foropening or closing said passage, and temperaturecontrolled means forsubstantially simultaneously adjusting said valve-means to increase thefuel flow and adjusting said damper-means toward closed position toincreaselthe air supply to the burner.

11. In combination, a burner, means for delivering a fluid fuel to theburner, valve-means controlling the flow of fuel to the burner, meansincluding a blower for delivering air under pressure to the burner,means including a passage for either admitting air under natural-draftto the burner or functioning to permit the escape of a portion of theair under pressure from the blower, a normally open damper-means foropening or closing said passage, and means for substantiallysimultaneously adjusting said valve-means toward or from a fully openposition and adjusting said damper-means toward or from a fully closedposition to proportionately increase or decrease the flow of fuel andair to the burner.

12. In combination, a burner, means for delivering a fluid fuel to theburner, valve-means controlling the flow of fuel to the burner, meansincluding a blower for delivering air under pres sure to the burner,means including a passage for admitting air under natural-draft to theburner and also functioning to permit the escape of air under pressurefrom the blower, normally open damper-means for opening or closing saidpassage, means for substantially simultaneously adjusting saidvalve-means to increase the fuel flow and adjusting said damper-meanstoward closed position to increase the air supply to the burner, andmeans for permitting opening movement of the valve-means only when theblower is functioning.

13. In combination, a burner, means for delivering a fluid fuel to theburner, valve-means controlling the flow of fuel to the burner, meansincluding a blower for delivering air under pressure to the burner,means including a passage for admitting air under natural-draft to theburner and also functioning to permit the escape of air under pressurefrom the blower, normally open damper-means for opening or closing saidpassage, means for substantially simultaneously adjusting saidvalve-means to increase the fuel flow and adjusting said damper-meanstoward closed position to increase the air supply to the burner, andmeans for causing the valve-means to reduce the fuel flow to a minimumwhen the blower ceases to function.

14. In combination, a burner, a chamber supplying air to the burner,means including a passage for delivering a fluid fuel to said burner,valve means for controlling the flow of fuel through the passage, meansfor supplying air under super-atmospheric pressure to the chamber, anair duct communicating with the chamher, a shutter in said duct, meansfor normally moving the shutter to open position to admit air throughthe duct to the chamber under atmospheric pressure, said shutter beingclosed by a super-atmospheric pressure in the chamber, and meansactuated by the closing movement of the shutter for increasing theopening of the fuel valve means.

15. In combination, a burner, a chamber supplying air to the burner,means including a passage for delivering a fluid fuel to said burner,valve means for controlling the flow of fuel through the passage, meansincluding a motordriven fan for supplying air under super-atmosphericpressure to the chamber, an air duct communicating with the chamber, ashutter in said duct adapted to be closed by the pressure in the chamberwhen the fan is operating, means for normally moving the shutter to openPosition to admit air to the chamber under natural draft when the fan isnot operating, and means actuated by a closing movement of the shutterfor increasing the opening of the fuel valve means.

16. In combination with a fluid-fuel burner, means for supplying fuel tothe burner including a. valve for controlling the rate of fuel supply tothe burner, a blower adapted to provide a substantially constant outputof air under pressure, and means for selectively directing a portion ofthis output to the burner for combustion air and venting the remainderof the blower output, said venting means also being effective to admitair to the burner under natural draft when the blower is not operatingso that the rate of supply of combustion air can be varied from naturaldraft up to the full output of the blower.

ARTHUR N. SCHREUDER.

